1. Field of the Invention
This invention relates generally to independent wheel suspension systems for motor vehicles and more particularly to a strut type independent rear suspension for a front wheel drive vehicle.
2. Disclosure Information
Rear suspension systems have been constructed to control the attitude of the rear wheels in order to provide particular handling characteristics of the motor vehicle, for example roll understeer or roll oversteer, as well as to provide a soft ride free from road vibrations. Handling characteristics such as roll understeer, roll oversteer, or roll neutral steer during cornering of a motor vehicle are achieved by controlling the toe angle of one of the rear wheels during the jounce stroke of the suspension.
U.S. Pat. No. 3,177,965 issued Apr. 13, 1965 and U.S. Pat. No. 3,202,237 which issued Aug. 24, 1965 disclose rear wheel suspensions in which a single trailing arm, a transverse driving axle half-shaft and a strut-type telescopic shock absorber with an integral coil spring are combined to produce toe control during wheel jounce. U.S. Pat. No. 3,893,701 issued July 8, 1975 achieves a similar result through the use of a flexible semi-trailing arm arrangement. None of these patents is directed toward the control of toe angle during wheel recession.
A vibration free ride is enhanced if the rear wheels are allowed to recess when the wheel hits a bump. However, both wheel recession and steering stability must be taken into account when designing a rear suspension. One way to take both factors into account is by controlling the toe angle of the wheel during its recession.
U.S. Pat. No. 3,759,542 issued Sept. 18, 1973 and U.S. Pat. No. 4,269,432 each disclose the use in rear suspensions of dual transverse control arms in combination with a tension strut to control toe angle during jounce and recession. As distinguished from the present invention, neither of these citations indicate the possibility of controlling toe angle through the use of properly selected resilient bushings. To the contrary, both disclosures teach that the use of elastomeric or resilient bushings to mount suspension control arms will in of itself cause at least the partial loss of toe angle control during wheel displacement.
One way to control the toe angle of a wheel is with a suspension having two control arms substantially transverse to the longitudinal axis of the vehicle. The arms control the toe angle changes of the wheels as they shift positions.
However, previous usage of the two transverse control arms in combination with a strut suspension necessitated the spring element in the strut suspension to be mounted about the strut.
In many strut suspensions, the spring has been positioned away from the strut and interposed between a transverse control arm and the chassis so that the strut upper mounted can be constructed from softer rubber, and secondly, valuable cargo space or engine compartment space can be maximized.